CollectionBase.ICollection.SyncRoot Property

Definition

Namespace:

System.Collections

Assembly:

System.Collections.NonGeneric.dll

Source:

CollectionBase.cs

Gets an object that can be used to synchronize access to the CollectionBase.

property System::Object ^ System::Collections::ICollection::SyncRoot { System::Object ^ get(); };

object System.Collections.ICollection.SyncRoot { get; }

member this.System.Collections.ICollection.SyncRoot : obj

 ReadOnly Property SyncRoot As Object Implements ICollection.SyncRoot

Property Value

Object

An object that can be used to synchronize access to the CollectionBase.

Implements

SyncRoot

Remarks

Derived classes can provide their own synchronized version of the CollectionBase using the SyncRoot property. The synchronizing code must perform operations on the SyncRoot of the CollectionBase, not directly on the CollectionBase. This ensures proper operation of collections that are derived from other objects. Specifically, it maintains proper synchronization with other threads that might be simultaneously modifying the CollectionBase object.

Enumerating through a collection is intrinsically not a thread safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

The following code example shows how to lock the collection using the SyncRoot during the entire enumeration:

// Get the ICollection interface from the CollectionBase
// derived class.
ICollection^ myCollection = myCollectionBase;
bool lockTaken = false;
try
{
    Monitor::Enter(myCollection->SyncRoot, lockTaken);
    for each (Object^ item in myCollection);
    {
        // Insert your code here.
    }
}
finally
{
    if (lockTaken)
    {
        Monitor::Exit(myCollection->SyncRoot);
    }
}

// Get the ICollection interface from the CollectionBase
// derived class.
ICollection myCollection = myCollectionBase;
lock(myCollection.SyncRoot)
{
    foreach (object item in myCollection)
    {
        // Insert your code here.
    }
}

' Get the ICollection interface from the CollectionBase
' derived class.
Dim myCollection As ICollection = myCollectionBase
SyncLock myCollection.SyncRoot
    For Each item As Object In myCollection
        ' Insert your code here.
    Next item
End SyncLock

Retrieving the value of this property is an O(1) operation.

See also

• IsSynchronized